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<span id="Guru-Real_002dto_002dreal-Transforms"></span><div class="header">
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<hr>
<span id="Guru-Real_002dto_002dreal-Transforms-1"></span><h4 class="subsection">4.5.5 Guru Real-to-real Transforms</h4>

<div class="example">
<pre class="example">fftw_plan fftw_plan_guru_r2r(int rank, const fftw_iodim *dims,
                             int howmany_rank,
                             const fftw_iodim *howmany_dims,
                             double *in, double *out,
                             const fftw_r2r_kind *kind,
                             unsigned flags);
</pre></div>
<span id="index-fftw_005fplan_005fguru_005fr2r"></span>

<p>Plan a real-to-real (r2r) multi-dimensional <code>FFTW_FORWARD</code>
transform with transform dimensions given by (<code>rank</code>, <code>dims</code>)
over a multi-dimensional vector (loop) of dimensions
(<code>howmany_rank</code>, <code>howmany_dims</code>).  <code>dims</code> and
<code>howmany_dims</code> should point to <code>fftw_iodim</code> arrays of length
<code>rank</code> and <code>howmany_rank</code>, respectively.
</p>
<p>The transform kind of each dimension is given by the <code>kind</code>
parameter, which should point to an array of length <code>rank</code>.  Valid
<code>fftw_r2r_kind</code> constants are given in <a href="Real_002dto_002dReal-Transform-Kinds.html">Real-to-Real Transform Kinds</a>.
</p>
<p><code>in</code> and <code>out</code> point to the real input and output arrays; they
may be the same, indicating an in-place transform.
</p>
<span id="index-flags-7"></span>
<p><code>flags</code> is a bitwise OR (&lsquo;<samp>|</samp>&rsquo;) of zero or more planner flags,
as defined in <a href="Planner-Flags.html">Planner Flags</a>.
</p>



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